1. Field of the Invention
The present invention relates to valves for equalizing pressure between two spaces of unequal pressure, and more particularly to a valve for equalizing the pressure between the enclosed space of an insulating glass unit and the ambient atmosphere.
2. Background of the Invention
Insulating glass units (xe2x80x9cIG unitsxe2x80x9d) have long been used in the building trades and other applications. Insulating glass units generally comprise at least two glass panes held in a generally parallel, spaced orientation by a peripheral spacer, the latter being joined to the sheets by a sealant. The space defined between the glass panes is hermetically sealed. High performance insulating glass is often manufactured using various technologies to improve energy efficiency, optical clarity and resistance to deterioration. The technology involving insulating glass units filled with a gas such as argon having a low coefficient of thermal conductivity is of particular interest.
Problems have been encountered with IG units carrying a gas such as argon in their between-pane spaces. Over a period of time, argon may slowly leak from the between-pane space to the atmosphere, and this generally occurs at a rate greater than the rate of permeation of air into the space, with the result that the pressure in the between-pane space reduced below atmospheric pressure. The resulting pressure differential causes the panes to cup inwardly, and the panes can eventually touch near their centers, with consequent loss of insulating value. In some cases, the cupping of the panes is so great as to cause one or the other of the panes to shatter. When failure occurs, the window units necessarily have to be replaced, and this can be extremely expensive in that the failed window unit must be removed and replaced with a new unit on a unit-by-unit basis.
Moreover, when IG units are transported to geographic locations of higher elevation and hence reduced atmospheric pressure, the panes of these IG units may bulge outwardly under the pressure differential across the panes, and this also causes distortion of the panes and may lead to ultimate glass breakage.
One possible remedy to this problem is to insert a valve in the insulating glass unit. A variety of valves or valve-like structures have been suggested to allow communication between the interior of insulating glass units and the ambient atmosphere. U.S. Pat. No. 4,567,703 (Ricks) discloses a spring-biased reusable valve intended to be opened over and over again whenever desired to equalize pressure between the interior of the insulating glass unit and the ambient atmosphere. U.S. Pat. No. 2,880,475 (Mills) discloses a self-sealing rubber valve. The Mills valve is designed to enable evacuation of the space between the panes of an insulating glass unit. The valve is configured similar to a duck bill valve, which accommodates the insertion of an exterior tube for release of interior pressure. U.S. Pat. No. 5,345,734 (Tremblay) discloses a plug to be inserted in the spacer at the periphery of an insulating glass unit. Once in place, the Tremblay plug is permanently sealed by the use of a plug similar in structure to a blind rivet.
Other examples of valve-like devices used in concert with insulating glass units are not truly valves at all in that they are designed to be sealed once and cannot be opened again under normal circumstances. Examples include U.S. Pat. No. 3,027,607 (Badger et al.), which discloses a metal insert to be embedded in the peripheral seal of the insulating glass unit to provide for gas injection and then to be permanently sealed with a bead of solder.
Additionally, U.S. Pat. No. 4,587,784 issued to Chavy et al discloses a structure similar to that of Badger that is intended to melt and release pressure within the IGU in the case of a structural fire. Under the heat of a fire, a fusible plug melts. Releasing increased pressure restrains the insulating glass unit from breaking.
U.S. Pat. No. 2,756,467 (Etling) shows the use of a hypodermic. needle passed through a sealant which forms a xe2x80x9cself healingxe2x80x9d seal when the needle is withdrawn. The Etling approach is intended to be used to evacuate the space within an insulating glass unit.
Finally, a number of prior art patents relate to the creation and sealing of pore holes which are intended to prevent the breakage of some types of insulating glass units in the manufacturing process. If an insulating glass unit is manufactured entirely of glass and the edges of the two panes are fused at their periphery, during the process of cooling the gases entrapped between the two panes contract dramatically creating a substantial possibility of breakage. Examples of a variety of pore holes and methods of sealing them are discussed in U.S. Pat. Nos. 2,784,462, 2,805,452, 2,887,737, 2,887,738, 2,894,294, 2,621,397, 2,886,864 and 2,755,521.
It would be desirable to be able manufacture an insulating glass unit, optionally containing an inert gas, such as argon, ship it to another location for further fabrication, storage or installation, and then have the capability to equalize the pressure in the insulating glass unit with the ambient atmosphere by either venting gas from the unit or allowing a gas such as air to enter the space between the panes. Furthermore, it would be desirable to be able to perform this function at anytime over the life of the insulating glass unit without undesired leakage occurring. Once pressure equalization is accomplished, it would be desirable to reseal the unit so as to prevent leakage of the entrapped gas.
The present invention relates to a pressure equalization valve utilized to equalize the pressure inside an insulating glass unit with the outside atmosphere. The pressure equalization valve of the present invention may be applied to one of the panes of an insulating glass unit so that the pressure within the between-pane space of the insulating glass unit may be equalized with the exterior, ambient pressure as and when needed.
The pressure equalization valve generally comprises a valve body having a stem for passing through an aperture in a glass pane, the body having an internal cavity and opposed, open ends to allow a gas to flow through it and also having an enlarged shoulder at one end for sealing engagement with a glass pane about the periphery of the aperture. The valve includes a valve plug that is received in the cavity and that is securably shiftable axially along its length between a plugged position preventing gas flow through the valve body and an unplugged position enabling such gas flow. xe2x80x9cSecurably shiftablexe2x80x9d means that the valve plug is prevented from accidentally escaping axially from the valve body when the plug is in its unplugged position. This feature is valuable in that it prevents the plug from being unintentionally removed or lost.
In a preferred embodiment, the internal cavity includes an internally threaded portion, and the valve plug includes an externally threaded portion that threadingly engages the internally threaded bore when the valve is in its plugged position. The plug further contains a second portion of lesser diameter but of greater axial length than the internally threaded bore of the valve body. Further, the valve plug preferably includes a third portion of a diameter preventing it from passing axially without rotation through the internally threaded bore. The lesser diameter second portion is intermediate the threaded first portion and the third portion such that when the first portion is unscrewed from the threaded bore, the space between the lesser diameter second, portion and the threaded bore provides a passageway for gas flow through the valve. Preferably, the third portion of the valve plug has exterior threads enabling it to be threadingly received in the threaded bore, thereby permitting the valve plug to be entirely unscrewed from the valve body.
The valve further preferably includes a washer assembly into which the end of the stem remote from its shoulder is received, the dimensions of the stem and the washer providing desirably for a secure press fit of the washer onto the system.
In the manufacturing process, an aperture is drilled through a glass pane, and the valve stem is inserted through the aperture from one side of the pane to bring the shoulder of the valve body into sealing engagement with the pane surface. The washer is received over the end of the stem on the other side of the pane and is secured to the stem, preferably through a press fit, thus sandwiching the glass pane securely between the shoulder and the washer. The valve plug may be part of the assembly thus secured to the glass pane, or it may be added after the plug body has been thus secured. Generally this placement of the valve will be accomplished before the panes are assembled into an insulating glass unit. The pane, with valve secured and preferably in its plugged position, is then employed in the assembly of an IG unit, the assembly commonly taking place in an atmosphere of e.g., argon to provide the unit with an argon filled between-pane space.
Once the insulating glass unit has been shipped to a desired location for installation the valve may be opened to allow the unit to xe2x80x9cbreathxe2x80x9d, thus equalizing the pressure across the panes. Once this occurs, the threaded plug may be tightened to seal the insulating glass unit. If desired, the threaded plug may then be disabled to prevent tampering which would cause loss or contamination of the retained gas. Optionally, a cap may be placed over the shouldered portion of the valve body to further protect the valve from tampering by unauthorized persons. The cap may, optionally, be decorative in design.